A Russian spy ship sailed a mere 30 miles from the Connecticut coast on Wednesday — lurking near a U.S. Navy base in Groton that is home to 15 nuclear submarines — during a tumultuous week for U.S.-Russian relations.

The U.S. Coast Guard has been tracking the Viktor Leonov as it moves along the U.S. coast in international waters. The ship had been spotted about 70 miles from Delaware’s shores on Monday.

Since the Russian vessel has not entered U.S. territory, which extends 12 miles into the ocean from the coast, officials have not taken action against it.

“We respect freedom of navigation exercised by all nations beyond the territorial sea of a coastal state consistent with international law,” the Coast Guard said in a statement.

News of the ship’s presence came just after President Donald Trump’s national security adviser Michael Flynn resigned Monday amid allegations that he may have illegally spoken to the Russian ambassador about U.S. sanctions.

Despite officials’ reassurance that the spy ship’s mission close to the U.S. is legal, some lawmakers condemned it as an overt display of Russian aggression.

“Anyone who would loiter off the coast of Connecticut isn’t doing it because of the great climate and weather — it’s freezing weather,” Joe Courtney (D-Conn.) said while addressing his colleagues in Congress Wednesday. “They are doing it with aggressive intent.”

“Russia is acting like it has a permission slip to expand influence, test limits of reach,” Sen. Chris Murphy (D-Conn.) added on Twitter.

A history of international travel

It’s not uncommon for foreign ships and aircraft to travel near the U.S. In September 2015, another Russian spy ship sailed close to King’s Bay in Georgia, where the U.S. Navy maintains another submarine base. That vessel, the Yanter, also approached the Florida coast, where it performed standard research mapping out the U.S.’s communication cables.

Around the same time, Chinese warships sailed close to Alaska, traveling through the Bering Sea as then-President Barack Obama visited the state.

Retired U.S. Navy officials insisted that the Leonov’s latest mission is also standard.

“I wouldn’t make a mountain out of a mole hill,” Retired Commander David Candler told the Hartford Courant. “It’s a ship, but it’s not the Great White fleet … These kinds of ships — and we do the same thing — go all over the place to stay reasonably accustomed to the waters.”

The U.S. also sends its ships close to other countries. On Friday, a U.S. missile destroyer was stationed in the Black Sea when four Russian aircraft buzzed by it at an “unsafe” distance, Pentagon officials said.

Repeated demands for investigation

The Leonov’s proximity to Connecticut marks the first time that a Russian ship has sailed so close to the U.S. since Trump took office, prompting some critics to question how the new administration — which has a complicated relationship with Moscow — may handle Russian aggression.

Rep. Rosa DeLauro (D-Conn.) demanded that Trump — who suggested on Twitter Wednesday that Obama was “too soft” on Russia — turn his attention to the ship instead of criticizing the previous administration.

“Russia is flexing its muscle and floating a submarine off the coast of Connecticut. Maybe you should focus your attention there?” she tweeted at the president.

Democrats suggested that the ship’s presence only reaffirms their demands for investigations into the Trump administration’s ties to Russia. Lawmakers have already called for both an extensive probe into Flynn’s talks with Russia and a 9/11-style commission to investigate allegations that Russia hacked the U.S. election to help Trump win the White House.

“This is a stark reminder of why we need a full account of Russia’s influence in the White House & meddling in our election,” Rep. John Larson (D-Conn.) tweeted.